PROJECT SUMMARY/ABSTRACT The proposed project aims to identify the optimal features of daytime napping and physical activity for cognition in older adults (K99) and examine the effects of an innovative, personalized behavioral intervention on promoting physical activity, healthy napping, sleep and cognitive function in sedentary older adults (R00). In the K99 phase, to ensure the successful completion of the R00 project and facilitate the achievement of my career development goals, I will follow an intensive training plan that incorporates courses, laboratory training, mentoring, and structured activities. In addition, a retrospective study will be conducted using two large longitudinal cohorts of older adults in the United States to examine the associations of daytime physical activity and nocturnal sleep with cognitive decline over 4-6 years. The K99 study will examine: 1) baseline associations of napping characteristics, physical activity and nocturnal sleep duration with cognition; 2) whether baseline napping, physical activity and nocturnal sleep duration predict cognitive decline at the 4-6 year follow-up; and 3) relationships between changes in physical activity and nocturnal sleep duration and changes in cognitive function at follow-up. Building off the K99, in the R00 phase, a randomized controlled trial will be conducted in older adults (without dementia) with both sedentary lifestyle and nocturnal sleep complaints to examine the effectiveness of a 24-week personalized behavioral intervention implemented with smartwatch technology on promoting physical activity, nocturnal sleep, and cognition compared against a control group; we have successfully tested this in a pilot study. Serum inflammatory biomarkers will be assessed to explore hypothesized mechanisms for associations among the study outcomes. In order to optimize outcomes at the subject level, a personalized physical activity plan will be calculated based on the individual?s characteristics, personal circadian rhythm at baseline, and the optimal characteristics of napping and physical activity that were identified in the K99 phase. The R00 study will examine: 1) whether the intervention increases participants? non-nap period physical activity, optimizes napping duration, and enhances nocturnal sleep; 2) whether the intervention improves participants? overall cognitive performance; 3) whether the relationship between the study intervention and cognitive performance is mediated by changes in physical activity, healthy nap duration, and nocturnal sleep duration; and 4) (exploratory aim) if the proposed intervention changes serum inflammatory biomarkers, including cytokines (IL-6, IL-1, TNF-?) and C-reactive protein, and whether these biomarkers relate to changes in physical activity, sleep, and cognitive function. Upon completion, this proposal will provide important insights on the optimal features of physical activity and napping for cognitive function. The proposed intervention may provide a novel way for older adults to optimize wellness and achieve active, healthy lives while aging, a key theme of the National Institute of Nursing Research in its mission to enhance public health. It will also build a strong foundation for my future career as an independent researcher.